In the hydrocarbon processing industry, many refineries recover valuable products from the heavy residual oil that remains after refining operations are completed. This recovery process is known as delayed coking and produces valuable distillates and coke in large vessels or coke drums. Coke drums are usually in operation in pairs so that when one coke drum is being filled with the byproduct or residual material, the feed may be directed to an empty drum so that the filled drum may be cooled and the byproduct purged from the coke drum, a process known as decoking. This allows the refinery process to operate in a continuous manner, without undue interruption.
When one coke drum is full, it must be purged of the byproduct fed into it. The drum is steam purged and cooled with quench water. The drum is then drained of water and vented to atmospheric pressure, after which the top and bottom heads are removed (i.e. the coke drum is de-headed) to allow the coke to be cut from the drum and fall into a catch basin, typically a rail car. This process of de-heading the coke drum can be extremely dangerous for several reasons. To mention only a few, the cooling water introduced into the hot drums prior to the removal of the bottom head becomes extremely hot and could leak from the loosened head and scald surrounding operators, the load of un-drained water and loose coke within the drum may exceed the limits of the support system and cause heavy equipment to fall, positioning the chute and necessary removal of the flanges or heads is done with operators who are in close proximity to the drums, potentially falling coke may injure workers as the heads are removed, and operating personnel may be exposed to finely divided coke particles, steam, hot water and noxious gases, when the drum is opened. Indeed several fatalities occur each year as a result of this manufacturing process. Once the coke is removed, the heads are replaced and the coke drum is prepared to repeat the cycle.